Fluid-cooled electrodes having permanent magnets to drive the arc therefrom and arc heater apparatus employing the same

ABSTRACT

An electrode has a tip forming an arcing surface, the tip being hollow, preferably generally annular in shape and preferably generally U-shaped in cross section. Disposed within the tip is according to one embodiment a permanent magnet having a contour similar to that of the tip, preferably having flat inside and outside walls, and which has the outside wall surface thereof forming either the north or south pole and the inside surface thereof forming the other magnetic pole. Lines of force leaving the magnet from, for example, the inside annular surface thereof being of the same polarity oppose each other and bend around the arcing surface of the tip to the pole formed by the outside wall surface of the permanent magnet. The magnetic field lines extend generally radially from the axis of the tip and transverse to the arcing surface, the lines also being transverse to the current in the arc path, and the field exerts a force on the arc which causes it to move substantially continuously around the arcing surface. The tip includes a passageway for the flow of the cooling fluid between the permanent magnet and the arcing surface to conduct heat flux therefrom, a wall portion of the tip separating the fluid passageway from the arcing surface. In another embodiment two annular permanent magnets radially spaced from each other have their upper and lower axially spaced surfaces forming the magnetic poles; a line between the north and south pole of each magnet may lie in a direction substantially parallel to the axis of the electrode, that is the axial ends of the magnets are the poles. The two magnets have their north and south poles oppositely disposed with respect to each other. The gap between the upper poles of the two radially spaced annular magnets is closed by an annular ring of ferromagnetic material. The magnetic field between opposing poles at the lower end surfaces of the magnets extends transverse to the arcing surface around the entire face or periphery of the arcing surface, said transverse magnetic field exerting a force on the arc which causes it to rotate or move substantially continuously. A third embodiment employs a ceramic coating over a portion of the arcing surface to limit the width of the track on which an arc path may be formed to thereby utilize only the portion of the arcing surface of the tip which has substantially the total magnetic field parallel thereto and extending radially thereacross. An additional embodiment uses peripherally spaced discrete radially extending bars, the inner ends of all bars having the same or like polarity. An arc heater has two axially spaced electrodes, each of which is fluid cooled and includes at least one annular permanent magnet in the electrode tip and passageway therein for the flow of cooling fluid.

United States Patent [72] Inventors Serafino M. DeCorso Media; James M.Wallace, Pittsburgh, both of Pa. [21] Appl. No. 4,488 [22] Filed Jan.21, 1970 [45] Patented Oct. 5, I971 [73] Assignee Westinghouse ElectricCorporation Pittsburgh, Pa.

[54] FLUID-COOLED ELECTRODES HAVING PERMANENT MAGNETS TO DRIVE THE ARCTHEREFROM AND ARC HEATER APPARATUS EMPLOYING THE SAME 18 Claims, 6Drawing Figs.

[52] US. Cl 13/18, 313/156 [51] int. Cl H05b 7/08 [50] Field of Search13/18;

[56] References Cited UNITED STATES PATENTS 2,286,21 l 6/1942 Dawson etal. l3/l 8 UX 3,369,067 2/1968 DeCorso 13/18 Primary Examiner-Bernard A.Gilheany Assistant Examiner-R. N. Envall, Jr. Anomeys-A. T. Stratton, C.L. Mcl'lale and M. l. Hull ABSTRACT: An electrode has a tip forming anarcing surface, the tip being hollow, preferably generally annular inshape and preferably generally U-shaped in cross section. Disposedwithin the tip is according to one embodiment a permanent magnet havinga contour similar to thatof the tip, preferably having flat inside andoutside walls, and which has the outside wall surface thereof formingeither the north or south pole and the inside surface thereof formingthe other magnetic pole. Lines of force leaving the magnet from, forexample, the inside annular surface thereof being of the same polarityoppose each other and bend around the arcing surface of the tip to thepole formed by the outside wall surface of the permanent magnet. Themagnetic field lines extend generally radially from the axis of the tipand transverse to the arcing surface, the lines also being transverse tothe current in the arc path, and the field exerts a force on the arewhich causes it to move substantially continuously around the arcingsurface. The tip includes a passageway for the flow of the cooling fluidbetween the permanent magnet and the arcing surface to conduct heat fluxtherefrom, a wall portion of the tip separating the fluid passagewayfrom the arcing surface. in another embodiment two annular permanentmagnets radially spaced from each other have their upper and loweraxially spaced surfaces forming the magnetic poles; a line between thenorth and south pole of each magnet may lie in a direction substantiallyparallel to the axis of the electrode, that is the axial ends of themagnets are the poles. The two magnets have their north and south polesoppositely disposed with respect to each other. The gap between theupper poles of the two radially spaced annular magnets is closed by anannular ring of ferromagnetic material. The magnetic field betweenopposing poles at the lower end surfaces of the magnets extendstransverse to the arcing surface around the entire face or periphery ofthe arcing surface, said transverse magnetic field exerting a force onthe are which causes it to rotate or move substantially continuously. Athird embodiment employs a ceramic coating over a portion of the arcingsurface to limit the width of the track on which an arc path may beformed to thereby utilize only the portion of the arcing surface of thetip which has substantially the total magnetic field parallel theretoand extending radially thereacross. An additional embodiment usesperipherally spaced discrete radially extending bars, the inner ends ofall bars having the same or like polarity. An arc heater hastwo axiallyspaced electrodes, each of which is fluid cooled and includes at leastone annular permanent magnet in the electrode tip and passageway thereinfor the flow of cooling fluid.

PATENTEU am 51971 $610,796

WITNESSES. INVENTORS Serofmo M. DeCorso a GBWMX K QJJQQMK James M.wqllqce.

, ATTORNEY PATENTED our 5191: 3510.796

' sum 2 or 2 FLUlD-COOLED ELECTRODES HAVING PERMANENT MAGNETS TO DRIVETHE ARC TIIEREFROM AND ARC HEATER APPARATUS EMPLOYING THE SAMECROSS-REFERENCE TO RELATED APPLICATIONS This application is related tothe copending application of Armin M.- Bruning for NonconsumableElectrode for Electric Arc Heating and Melting and Methods, Ser. No.866,274, filed Oct. 14, 1969 and assigned to the assignee of the instantinvention, which'is a continuation-in-part of application Ser. No.407,332, filed Oct. 29, 1964, now abandoned.

BACKGROUND OF THE INVENTION I magnet located near an arcing surface butnot within the tip,

with its north and south poles axially spaced, be used to move an arc;such a suggestion was made in application Ser. No. 407,332, filed Oct.29, 1964.

, A number of patents have issued on prior art electrodes in which amagnetic field coil is located in a tip generally annular in'shape andgenerally U-shaped in cross section, with a fluid passageway U-shaped incross section extending around the entire tip to conduct cooling fluidnear the arcing surface and remove heat flux therefrom. Such prior artelectrodes with field coils are exemplified by Pat. No. 3,369,068 to P.F. Kienast issued Feb. 13, 1968,v and Pat. No. 3,398,229 to Decorso etal. issued Aug. 20, 1968.

Such prior art electrodes employing field coils for setting up magneticfields to rotate the are are complicated by the necessity ofprovidingelectrical insulation between the magnetic field coil and theelectrode structure, and require that leads for energizing the fieldcoil pass through at least a portion of the electrode structure andusually pass the entire long distance between the electrode tip and theupper or head portion of the electrode. Furthermore, magnetic fieldcoils are relatively expensive compared to permanent magnets.

Additionally, magnetic field coils almost always have the north andsouth poles of the coil disposed with respect to each other in adirection parallel to the longitudinal axis of the electrode, with theresult that many flux lines leave the electrode tip in a direction whichis substantially perpendicular to the arcing surface rather thantransverse to the arc path; the magnetic field over the arcing surfaceis nonuniform and there is a tendency for the arc to be driven towardthe inside annular surface of the electrode tip as a result of theconfiguration of the magnetic field lines, or more precisely, the shapeof the magnetic field, density, and strength of field components incertain directions.

SUMMARY OF THE INVENTION Our electrode employing a permanent magnet ischeaper than prior art structures, needs no electrical insulation orelectrical connections toa field coil, and furthermore in our electrodeemploying a permanent magnet with the north and south poles of themagnet being selectively the outside annular surface and the insideannular surface, or vice versa, we produce a magnetic field whichextends transversely to (substantially radially across) a much largerportion of the arcing surface of the electrode tip. This is also true ofother embodiments of for invention. An arc heater having electrodesembodying our invention is very simple and easy to construct compared toprior art are heaters.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a vertical section partiallybroken away through an electrode and-electrode tip according to oneembodiment of our invention;

FIG. 2 is a section through the lines 11-1] of FIG. 1;

FIG. 3 is an electrode tip partially broken away according to a secondembodiment of our invention in which two radially spaced annularpermanent magnets are employed;

FIG. 4 is an additional embodiment of our invention employing tworadially spaced annular permanent magnets;

FIG. 5 is a cross-sectional view through an arc heater employingelectrodes according to our invention in which annular or ring-shapedpermanent magnets are mounted in the tips of the electrodes; and

FIG. 6 shows schematically segmented pennanent magnet field producingmeans including peripherally spaced radially extending bars all havingthe same magnetic pole at the inner ends thereof.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. I the electrodegenerally designated 1 1 is seen to include a supporting column portiongenerally designated 12 and an electrode tip generally designated 13.The supporting column is shown as consisting of two coaxially mountedtubes 14 and 15, the tubes being radially spaced from each other toprovide a cylindrical fluid flow passageway 16 therebetween. The outertube 14 has a flaring transverse flange portion 17 at the lower endthereof with threads 18 to receive in threaded engagement the electrodetip generally designated 13. An 0- ring 20 disposed within a suitableannular groove provides a fluidtight seal.

The electrode tip' generally designated 13 includes an annular shellcomposed of material having high thermal and electrical conductivitywith an outer wall portion 24 of larger diameter and an inner wallportion 25 of smaller diameter, and an annular bottom portion 26, shownas curved with the inner and outer edges being extensions of wallportions 25 and 24. Lead 28 symbolizes means for connecting theelectrode to one terminal of a source of potential, the other terminalof opposite polarity being connected to a melt 30 which is at leastpartially conductive, cylinder 14 being conductive for bringing currentto the tip to produce the are 33 from the tip to the melt. An axialportion of the outside surface of outer wall 24 is coated with a ceramiccoating 35 to provide thermal insulation.

The aforementioned tubular member 15 of the supporting column providesinside thereof a fluid passageway 37 and is seen to have at the lowerend thereof a thickened flaring portion 40 of considerably enlargedoutside diameter which has the outside wall 42 thereof spaced from theinside surface of outer wall 24 of the electrode tip to form acylindrical passageway 44 which extends around the entire tip, whichpassageway 44 communicates at one end thereof with the aforementionedcylindrical passageway 16 between the tubular support members 14 and 15,and communicates at the other end thereof with passageway 37.

The lower end portion of enlarged diameter 40 is terminated at apredetermined axial position with respect to the electrode and tip andhas secured to the lower surface 46 thereof by any convenient means, notshown for convenience of illustration, a permanent magnet generallydesignated 48. Member 15 including portion 40 may be made of iron andmagnet 48 secured thereto by magnetic attraction. On the other hand,where considerations of magnetic field strength at the arcing surfacemake a low reluctance path within the tip the tip, the bottom of themagnet 48 also being spaced from the adjacent inner surface of theelectrode tip so as not to ob struct the aforementioned fluid flowpassageway 44 which ex- 5 tends around the permanent magnet on threesides thereof and around the entire tip, passageway 44 as aforementionedcommunicating at the inside annular opening thereof with the passageway37 in cylinder 15, forming a complete fluid flow passageway forconducting cooling fluid near the arcing surface 29 in a path U-shapedin cross section which extends annularly around the entire tip, thecoolant entering one and thereafter being removed through the otherfluid flow passageway in the supporting structure generally designatedIt will be understood that tube is illustrated as supported from aboveand held in position by means, not shown for convenience ofillustration, to thereby maintain the permanent magnet 48 in desiredposition within the tip and spaced therefrom, although other long knownand conventional spacing means could be employed, such for example asspaced studs so positioned as not to substantially impede the flow ofcooling fluid.

Permanent magnet 48 by way of illustration has the outside substantiallyflat annular surface 51 thereof forming the north pole of the magneticstructure and the inside substantially flat annular wall surface 52thereof forming the south magnetic pole. Lines of force of similarpolarity leaving or entering the inside wall surface 52 of the magnetare repelled from each other because of their like polarity, are bentaround the arcing surface of the electrode, and enter the magnet againat the surface of opposite polarity 51, these lines of force beingillustrated at 57 and 58. 1t will be understood that the north and southpoles may be reversed if desired.

The permanent magnet may be composed of ferrite material or ceramicmaterial and by suitable choice of material and dimensions may supply amagnetic field having a strength or flux density, when the field emergesfrom the magnetic pole surfaces, of several thousand gauss, which isample to cause rotation of the are at a speed which prevents substantialerosion of material from the arcing surface, the force exerted on thearc and the speed of rotation thereof being a function of the product ofthe magnetic field strength and the arc current.

Particular reference is made to FIG. 2, a cross section along the linell-ll of FIG. 1. The annular passageway 44 is seen both on the outsideand inside of the permanent magnet 48. The hollow central depression inthe electrode tip resulting from its annular ring configuration is seenat 61.

Particular reference is made now to FIG. 3 which shows an electrodeaccording to a second embodiment of our invention, only one half of thetip being shown as needed to fully illustrate this embodiment of theinvention. In FIG. 3 the shell of the tip is shown at 65 having anannular substantially flat bottom portion forming an arcing surface witha recessed control closure portion 85, and disposed within the shell areradially spaced permanent magnets 71 and 72 both being in the form ofrings with their upper ends oppositely poled as shown, the magnets beingseparated by an annular spacer member 73 composed of any suitablediamagnetic material such for example as epoxy resin. An annular ringcomposed of iron or other ferromagnetic material is shown at 75 closingthe flux path internal to the electrode. Members 71, 72, 73 and 75 arespaced from the adjoining inside walls of the shell 65 to provide afluid passageway 77 around the entire tip for the flow of cooling fluidto conduct heat flux from the arcing surface. Any suitable means, notshown for convenience of illustration, may be employed for holding thetwo annular permanent magnets, the spacer 73, and the iron ring member75 in position within the electrode tip. The fluid in passageway 77which communicates with passageway 16, now shown, passes through thecylindrical space 79 within magnet ring 72, thence through the centralpassageway 80 of the iron ring 75 and into a passageway, not shown,corresponding to passageway 37, FIG. 1. As aforementioned, the upperopening at the outside portion of passageway 77 it is understoodcommunicates with a fluid channeling passageway, not shown forconvenience of illustration, between coaxially aligned cylinders andcorresponding to passageway 16, FIG. 1.

The magnetic field illustrated at 81 extends between the lower southpole of outer ring magnet 71 and the lower north pole of inner ringmagnet 72, extends across or transverse to the arcing surface andtransverse to the arc path and exerts a force on the arc according tothe left-hand rule or Fleming's rule which causes the arc to rotate inan annular path around the arcing surface. A ceramic heat shield 83covers a portion of the outside wall of shell 65 which will not be usedas part of the arcing surface. In FIG. 3 in addition to the ceramiccoating or other heat shield material 83, the central hub portion 85 ofthe shell 65 is seen to be covered by coating 86 of ceramic or otherrefractory material to assist in protecting the portion 85 from heat ofradiation and convection of the arc and hot gases, since this portion 85may not be as well cooled by the circulating fluid as are the portionsof the electrode tip and shell adjacent the U-shaped passageway 77.

The relating polarities of magnets 71 and 72 may be reversed, ifdesired.

Particular reference is made now to FIG. 4. The shell 88 forming the tipmay be substantially cylindrical in shape and the magnets 71 and 72' areseparated by the spacer 73' of diamagnetic material and the iron ring75' provides a closed flux path within the electrode. [t is understoodthat members 71, 72', 73 and 75' are supported and maintained inposition by any suitable means, not shown for convenience ofillustration. A ceramic coating 83' extends along the entire length ofthe outside wall of shell 88 and extends a predetermined distance towardthe axial center of the tip as shown. A discshaped coating 91 of ceramicmaterial is also provided on the under surface of the tip, the outeredge of the disc-shaped portion 91 being spaced from the inwardlyextending edge of ceramic coating 83' to provide an exposed arcingsurface 93 of predetermined width from which the are 94 takes place. Themagnetic field is shown at 95; it is seen to extend between member 71'and 73' transversely across the arcing surface 93 and exerts a force onthe are which causes the are 94 to rotate in a substantially annularpath around the arcing surface.

Particular reference is made to FIG. 5 in which an arc heater is shownemploying two axially spaced electrodes, both being similar to theelectrode of FIG. 1 and generally designated 101 and 102 respectively.Electrode 101 has a tip 104, a permanent magnet 105, and a fluidpassageway 106. Electrode 101 is held in position within the pressurevessel 108 by an annular ring and supporting member 110 electricallyinsulated from the electrode by an insulating sleeve 111. The ringsupport and spacing member 110 has a plurality of peripherally spacedbores or passageways extending axially therethrough, two of these beingshown at 112 and 113, for admitting gas to be heated into the arcchamber 114 between the electrodes.

The aforementioned second electrode 102, which is the downstreamelectrode, has a tip 116, a permanent magnet 117, and a passageway 118for the flow of cooling fluid. Leads 121 'and 122 connect the electrodes101 and 102 to terminals of opposite polarity of a source of potentialto produce and sustain the are 123 between electrodes. Theaforementioned downstream electrode 102 is mounted and held in positionwithin the pressure vessel 108 by an annular ring member 124 which maybe composed of insulating material or may be composed of metal in whichcase a sleeve 125 composed of electrically insulating material isinterposed between the electrode and the support member 124.

The construction of the downstream electrode differs slightly from thatof the upstream electrode. The central opening formed by the annularring configuration of the tip 104 of electrode 101 is seen to be closedat 127, whereas the inside wall of the smaller diameter of the tip orshell 116 of electrode 102 forms a cylindrical space in which is fixedlysecured a generally cylindrical nozzle member 129 having an exhaust vent130 communicating between the arc chamber 114 and the outside of thepressure vessel, and through which gas heated by the are 123 exits fromthe arc heater.

In the operation of the apparatus of FlG. 5 the two ringshaped permanentmagnets may be poled as shown, magnet 105 setting up a field which istransverse to the arcing surface of tip 104 and magnet 117 of electrode102 setting up a magnetic field which is transverse to the arcingsurface of tip 116. It is seen that the inside wall surface of smallerdiameter of magnet 105 has the same magnetic polarity as the inside wallsurface of smaller diameter of magnet 117; the field is set up at thetwo electrodes tend to oppose each other and enhance the strength of thetransverse component of the field which lies across each arcing surface.Both magnets exert a force on the are 123 which cause the arc to rotatein an annular path between electrodes. It is to be noted that the forcesexerted on the 'arc 123 by the two magnets are such as to add and causethe are 123 to rotate in the same angular direction between electrodes.

ln accordance with long-established practice, the permanent magnets maybe solid or laminated solid magnets being shown for ease ofillustration.

Particular reference is made to FIG. 6. Discrete radially extendingperipherally spaced magnetic bars 150, which may extend perpendicular tothe axis of the electrode, have all their inner ends of like polarityand all their outer ends of like polarity. A magnetic field transverseto the arcing surface and similar to fields 57 and 58, FIG. 1, is setup. Preferably the bars extend at least the major portion of thedistance between the wall of smaller diameter of the tip and the wall oflarger diameter of the tip. lnthe arc heater of FIG. 5, the permanentmagnet configurations and tip configurations of FIGS. 3 and 4 may besubstituted for those shown.

The foregoing written description and the drawings are illustrative onlyand are not to be interpreted in a limiting sense.

we claim as our invention:

1. An electrode comprising, in combination, an electrode tip forming anarcing surface, the tip being hollow and generally cylindrical in shape,a supporting column for the electrode tip secured thereto, permanentmagnet means mounted within the electrode tip and spaced from theadjacent inner wall surfaces of the tip at all points therearound toprovide a passageway within the tip between the permanent magnet meansand the wall of the tip for the flow of cooling fluid to conduct heatflux from the tip, the electrode being adapted to be connected to aterminal of one polarity of a source of potential to produce an are fromthe tip to a surface of opposite polarity, the permanent magnet meanswithin the tip setting up a magnetic field which is transverse to thearcing surface and which has lines of force which extend in a radialdirection from the axis of the tip, said magnetic field exerting a forceon the are which causes thearc to move substantially continuously aroundthe arcing surface of the tip.

2. An electrode according to claim 1 in which said tip is additionallycharacterized as being annular in shape and generally U-shaped in crosssection with an outer wall portion of larger diameter and an inner wallportion of relatively smaller diameter, and the permanent magnet meansis a single ring-shaped permanent magnet disposed within the tip andspaced therefrom'to provide said fluid flow passageway, one magneticpole surface of the permanent magnet being the inside annular wall ofsmaller diameter thereof and the other magnetic pole surface of thepermanent magnet being the outside annular wall of larger diameterthereof, the permanent magnet setting up a magnetic field transverse tothe arcing surface around the entire tip, said transverse magnetic fieldcausing the are therefrom to rotate.

3. An electrode according to claim 2 in which the supporting column isadditionally characterized as including two radially spaced coaxiallyaligned tubes forming a cylindrical fluid flow passageway therebetweenwhich communicates with the passageway within the tip, the inner of saidtubes having at the lower end thereof a portion of substantiallyincreased outside diameter with a bottom surface contoured to receivethe upper surface of the permanent magnet and ,to support the permanentmagnet in position within the tip.

4. An electrode according to claim I in which the permanent magnet meansincludes first and second radially spaced coaxially aligned annularpermanent magnets 0ppositely poled with respect to each other in anaxial direction, and diamagnetic spacer means interposed between thefirst and second permanent magnets, the first and second permanentmagnets and the spacer means all being spaced from the adjacent wallportions of the tip to provide said fluid flow passageway.

5. An electrode according to claim 4 additionally characterized ashaving a coating of refractory material on the outside surface of thetip wall, said coating extending on the bottom of the tip inwardly apredetennined distance and terminating along a circular line apredetermined radial distance from the axis of the tip, additionalrefractory material covering the central portion of the bottom of thetip and extending a predetermined radial distance from the axis thereofto terminate in a circular line of smaller radius than said first namedcircular line to thereby form an exposed arcing surface portion of thetip annular in shape and of a predetermined width extending around theentire electrode, the are from the tip taking place from said last-namedportion, the magnetic field between the first and second permanentmagnets extending transversely across said arcing surface portion.

6. In an electrode adapted to be connected to a terminal of one polarityto produce an arc to a surface of opposite polarity, of the type havinga fluid-cooled tip generally annular in shape and generally U-shaped incross section with an outer generally annular wall of larger diameterand an inner generally annular wall of smaller diameter, with magneticfield producing means in the tip for producing a field which exerts aforce on an are from the tip and causes said are to move substantiallycontinuously around the tip, the improvement which comprises a permanentmagnet in the tip for setting up said magnetic field, the permanentmagnet being spaced from .adjacent inside wall surfaces of the tip toprovide a passageway for the flow of cooling fluid, the permanent magnetbeing generally annular in shape with an outside wall of larger diameterand an inside wall of relatively smaller diameter, the outside wall ofthe magnet forming one magnetic pole around the entire periphery thereofand the inside wall of the magnet .forming the other magnetic polearound the entire periphery thereof, the lines of force of the magneticfield extending generally radially from the axis of the magnet andtransverse to the arcing surface.

7. In an electrode adapted to be connected to a terminal of one polarityto produce anarc to a surface of opposite polarity, of the type having afluid-cooled tip generally annular in shape and generally U-shaped incross section with an'outer generally annular wall of larger diameterand an inner generally annular wall of smaller diameter, with magneticfield producing means in the tip for producing a field which exerts aforce on an are from the tip and causes said arc to move substantiallycontinuously around the tip, the improvement which comprises permanentmagnet means in the tip for setting up said magnetic field, thepermanent magnet means consisting of a plurality of substantiallyaxially aligned peripherally spaced bar magnets each extending in aradial direction from the axis of the tip and extending at least a majorportion of the distance between the wall of smaller diameter and thewall of larger diameter of the tip, all of the bar magnets having theends thereof adjacent the wall of smaller diameter of the same magneticpolarity and all of the bar magnets having the ends thereof adjacent thewall of larger diameter of the sameopposite magnetic polarity, the linesof force of the magnetic field extending generally radially from theaxis of the tip and transverse to the arcing surface.

8. In an electrode adapted to be connected to a terminal of one polarityto produce an arc to a surface of opposite polarity of the type having afluid-cooled tip generally annular in shape and generally U'shaped incross section with an outer generally annular wall of large diameter andan inner generally annular wall of relatively smaller diameter, withmagnetic field force on an are from the tip and causes said are to movesubstantially continuously around the tip, the improvement whichcomprises permanent magnet means in the tip for setting up said magneticfield, the permanent magnet means including two radially spacedcoaxially aligned permanent ring magnets each having axially spacedmagnetic poles at the upper and lower surfaces thereof, the two ringmagnets being oppositely poled with respect to each other, the ringmembers being spaced from adjacent inside wall surfaces of the tip toprovide a passageway within the tip for the flow of cooling fluid, themagnetic lines of force between the lower magnetic pole of one ringmagnet and the other opposite lower magnetic pole of the other ringmagnet extending generally radially from the axis of the ring magnetsand transverse to the arcing surface.

9. An electrode according to claim 8 including in addition a ring ofiron or other ferromagnetic material extending between the top surfacesof both thering magnets and forming a closed magnetic circuit betweenthe upper poles of both ring magnets.

10. An electrode according to claim 8 including in addition ring spacermeans composed of diamagnetic material interposed between and spacingthe two ring magnets from each other, said spacer means being spacedfrom adjacent inside wall surfaces of the top and bottom of the tip.

11. An electrode comprising, in combination, a generally cylindricalelectrode tip having at least a partially closed bottom and forming anarcing" surface, the electrode tip having at least one space thereinextending around the entire periphery of the tip, at least a portion ofthe space forming fluid passageway for the flow of cooling fluid toconduct heat flux from the arcing surface, at least one permanent magnetmounted in the tip and occupying at least some of the remainder of thespace in the tip, and a supporting column for the tip secured theretoand including means for conducting fluid to and from the passageway inthe tip, the electrode being adapted to be connectedto a terminal of onepolarity of a source of potential to produce an are from the tip to asurface of opposite polarity, the permanent magnet within the tipsetting up a magnetic field which is transverse to the arcing surfaceand which has lines of force which extend in a radial direction from theaxis of the tip, said magnetic field exerting a force on the are whichcauses the arc to move substantially continuously around and over thearcing surface of the tip.

12. An electrode according to claim If in which the permanent magnet isring-shaped with a substantially flat inner wall surface of smallerdiameter and a substantially flat outer wall surface of larger diameter,the wall surfaces being substantially parallel to the axis of theelectrode, the inner wall surface and the outer wall surface forming theopposite magnetic poles of the permanent magnet.

13. An electrode according to claim 11 including two radially spacedsubstantially axially aligned permanent magnets mounted within the spacewithin the electrode tip, the axial end surfaces of both permanentmagnets forming the magnetic poles thereof, the poles of one magnetbeing oppositely disposed with respect to the corresponding poles of theother magnet.

14. An electrode according to claim 13 including in addition diamagneticmeans mounted between the two permanent magnets and spacing the samefrom each other.

15. An electrode according to claim 14 in which the diamagnetic meansspacing the two permanent magnets is an epoxy resin.

16. An electrode according to claim 13 including in addition a coatingof ceramic material covering at least a portion of the arcing surface tolimit the width of the arc track as the arc moves around and over thearcing surface.

17. An electrode according to claim 13 including in addition a polepiece across the top ends of both permanent magnets forrning a lowreluctance path.

18. An electrode according to claim 11 in which the permanent magnetconsists of a plurality of radially extending bar magnets disposedaround the entire periphery of the tip at peripherally spaced intervals,all of the inner ends of the bar magnets being of like magneticpolarity.

1. An electrode comprising, in combination, an electrode tip forming anarcing surface, the tip being hollow and generally cylindrical in shape,a supporting column for the electrode tip secured thereto, permanentmagnet means mounted within the electrode tip and spaced from theadjacent inner wall surfaces of the tip at all points therearound toprovide a passageway within the tip between the permanent magnet meansand the wall of the tip for the flow of cooling fluid to conduct heatflux from the tip, the electrode being adapted to be connected to aterminal of one polarity of a source of potential to produce an arc fromthe tip to a surface of opposite polarity, the permanent magnet meanswithin the tip setting up a magnetic field which is transverse to thearcing surface and which has lines of force which extend in a radialdirection from the axis of the tip, said magnetic field exerting a forceon the arc which causes the arc to move substantially continuouslyaround the arcing surface of the tip.
 2. An electrode according to claim1 in which said tip is additionally characterized as being annular inshape and generally U-shaped in cross section with an outer wall portionof larger diameter and an inner wall portion of relatively smallerdiameter, and the permanent magnet means is a single ring-shapedpermanent magnet disposed within the tip and spaced therefrom to providesaid fluid flow passageway, one magnetic pole surface of the permanentmagnet being the inside annular wall of smaller diameter thereof and theother magnetic pole surface of the permanent magnet being the outsideannular wall of larger diameter thereof, the permanent magnet setting upa magnetic field transverse to the arcing surface around the entire tip,said transverse magnetic field causing the arc therefrom to rotate. 3.An electrode according to claim 2 in which the supporting column isadditionally characterized as including two radially spaced coaxiallyaligned tubes forming a cylindrical fluid flow passageway therebetweenwhich communicates with the passageway within the tip, the inner of saidtubes having at the lower end thereof a portion of substantiallyincreased outside diameter with a bottom surface contoured to receivethe upper surface of the permanent magnet anD to support the permanentmagnet in position within the tip.
 4. An electrode according to claim 1in which the permanent magnet means includes first and second radiallyspaced coaxially aligned annular permanent magnets oppositely poled withrespect to each other in an axial direction, and diamagnetic spacermeans interposed between the first and second permanent magnets, thefirst and second permanent magnets and the spacer means all being spacedfrom the adjacent wall portions of the tip to provide said fluid flowpassageway.
 5. An electrode according to claim 4 additionallycharacterized as having a coating of refractory material on the outsidesurface of the tip wall, said coating extending on the bottom of the tipinwardly a predetermined distance and terminating along a circular linea predetermined radial distance from the axis of the tip, additionalrefractory material covering the central portion of the bottom of thetip and extending a predetermined radial distance from the axis thereofto terminate in a circular line of smaller radius than said first namedcircular line to thereby form an exposed arcing surface portion of thetip annular in shape and of a predetermined width extending around theentire electrode, the arc from the tip taking place from said last-namedportion, the magnetic field between the first and second permanentmagnets extending transversely across said arcing surface portion.
 6. Inan electrode adapted to be connected to a terminal of one polarity toproduce an arc to a surface of opposite polarity, of the type having afluid-cooled tip generally annular in shape and generally U-shaped incross section with an outer generally annular wall of larger diameterand an inner generally annular wall of smaller diameter, with magneticfield producing means in the tip for producing a field which exerts aforce on an arc from the tip and causes said arc to move substantiallycontinuously around the tip, the improvement which comprises a permanentmagnet in the tip for setting up said magnetic field, the permanentmagnet being spaced from adjacent inside wall surfaces of the tip toprovide a passageway for the flow of cooling fluid, the permanent magnetbeing generally annular in shape with an outside wall of larger diameterand an inside wall of relatively smaller diameter, the outside wall ofthe magnet forming one magnetic pole around the entire periphery thereofand the inside wall of the magnet forming the other magnetic pole aroundthe entire periphery thereof, the lines of force of the magnetic fieldextending generally radially from the axis of the magnet and transverseto the arcing surface.
 7. In an electrode adapted to be connected to aterminal of one polarity to produce an arc to a surface of oppositepolarity, of the type having a fluid-cooled tip generally annular inshape and generally U-shaped in cross section with an outer generallyannular wall of larger diameter and an inner generally annular wall ofsmaller diameter, with magnetic field producing means in the tip forproducing a field which exerts a force on an arc from the tip and causessaid arc to move substantially continuously around the tip, theimprovement which comprises permanent magnet means in the tip forsetting up said magnetic field, the permanent magnet means consisting ofa plurality of substantially axially aligned peripherally spaced barmagnets each extending in a radial direction from the axis of the tipand extending at least a major portion of the distance between the wallof smaller diameter and the wall of larger diameter of the tip, all ofthe bar magnets having the ends thereof adjacent the wall of smallerdiameter of the same magnetic polarity and all of the bar magnets havingthe ends thereof adjacent the wall of larger diameter of the sameopposite magnetic polarity, the lines of force of the magnetic fieldextending generally radially from the axis of the tip and transverse tothe arcing surface.
 8. In an electrode adapted to be connected to aterminal of one polarity to produce an arc to a surface of oppositepolarity of the type having a fluid-cooled tip generally annular inshape and generally U-shaped in cross section with an outer generallyannular wall of large diameter and an inner generally annular wall ofrelatively smaller diameter, with magnetic field producing means in thetip for producing a field which exerts a force on an arc from the tipand causes said arc to move substantially continuously around the tip,the improvement which comprises permanent magnet means in the tip forsetting up said magnetic field, the permanent magnet means including tworadially spaced coaxially aligned permanent ring magnets each havingaxially spaced magnetic poles at the upper and lower surfaces thereof,the two ring magnets being oppositely poled with respect to each other,the ring members being spaced from adjacent inside wall surfaces of thetip to provide a passageway within the tip for the flow of coolingfluid, the magnetic lines of force between the lower magnetic pole ofone ring magnet and the other opposite lower magnetic pole of the otherring magnet extending generally radially from the axis of the ringmagnets and transverse to the arcing surface.
 9. An electrode accordingto claim 8 including in addition a ring of iron or other ferromagneticmaterial extending between the top surfaces of both the ring magnets andforming a closed magnetic circuit between the upper poles of both ringmagnets.
 10. An electrode according to claim 8 including in additionring spacer means composed of diamagnetic material interposed betweenand spacing the two ring magnets from each other, said spacer meansbeing spaced from adjacent inside wall surfaces of the top and bottom ofthe tip.
 11. An electrode comprising, in combination, a generallycylindrical electrode tip having at least a partially closed bottom andforming an arcing surface, the electrode tip having at least one spacetherein extending around the entire periphery of the tip, at least aportion of the space forming fluid passageway for the flow of coolingfluid to conduct heat flux from the arcing surface, at least onepermanent magnet mounted in the tip and occupying at least some of theremainder of the space in the tip, and a supporting column for the tipsecured thereto and including means for conducting fluid to and from thepassageway in the tip, the electrode being adapted to be connected to aterminal of one polarity of a source of potential to produce an arc fromthe tip to a surface of opposite polarity, the permanent magnet withinthe tip setting up a magnetic field which is transverse to the arcingsurface and which has lines of force which extend in a radial directionfrom the axis of the tip, said magnetic field exerting a force on thearc which causes the arc to move substantially continuously around andover the arcing surface of the tip.
 12. An electrode according to claim11 in which the permanent magnet is ring-shaped with a substantiallyflat inner wall surface of smaller diameter and a substantially flatouter wall surface of larger diameter, the wall surfaces beingsubstantially parallel to the axis of the electrode, the inner wallsurface and the outer wall surface forming the opposite magnetic polesof the permanent magnet.
 13. An electrode according to claim 11including two radially spaced substantially axially aligned permanentmagnets mounted within the space within the electrode tip, the axial endsurfaces of both permanent magnets forming the magnetic poles thereof,the poles of one magnet being oppositely disposed with respect to thecorresponding poles of the other magnet.
 14. An electrode according toclaim 13 including in addition diamagnetic means mounted between the twopermanent magnets and spacing the same from each other.
 15. An electrodeaccording to claim 14 in which the diamagnetic means spacing the twopermanent magnets is an epoxy resin.
 16. An electrode according to claim13 includIng in addition a coating of ceramic material covering at leasta portion of the arcing surface to limit the width of the arc track asthe arc moves around and over the arcing surface.
 17. An electrodeaccording to claim 13 including in addition a pole piece across the topends of both permanent magnets forming a low reluctance path.
 18. Anelectrode according to claim 11 in which the permanent magnet consistsof a plurality of radially extending bar magnets disposed around theentire periphery of the tip at peripherally spaced intervals, all of theinner ends of the bar magnets being of like magnetic polarity.